[PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[H.J. Lu]

Add -fextra-libc-function=memcmpeq to map

extern int __memcmpeq (const void *, const void *, size_t);

which was added to GLIBC 2.35, to __builtin_memcmp_eq.

gcc/

	* builtins.cc: Include "opts.h".
	(expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
	available.
	* builtins.def (BUILT_IN___MEMCMPEQ): New.
	* common.opt: Add -fextra-libc-function=.
	* opts.cc (extra_libc_functions): New.
	(parse_extra_libc_function): New function.
	(common_handle_option): Handle -fextra-libc-function=.
	* opts.h (extra_libc_function_list): New.
	(extra_libc_functions): Likewise.
	* doc/invoke.texi: Document -fextra-libc-function=memcmpeq.

gcc/testsuite/

	* c-c++-common/memcmpeq-1.c: New test.
	* c-c++-common/memcmpeq-2.c: Likewise.
	* c-c++-common/memcmpeq-3.c: Likewise.
	* c-c++-common/memcmpeq-4.c: Likewise.
	* c-c++-common/memcmpeq-5.c: Likewise.
	* c-c++-common/memcmpeq-6.c: Likewise.
	* c-c++-common/memcmpeq-7.c: Likewise.
---
 gcc/builtins.cc                         |  5 ++++-
 gcc/builtins.def                        |  4 ++++
 gcc/common.opt                          |  4 ++++
 gcc/doc/invoke.texi                     |  6 ++++++
 gcc/opts.cc                             | 23 +++++++++++++++++++++++
 gcc/opts.h                              |  7 +++++++
 gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
 13 files changed, 125 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c

diff --git a/gcc/builtins.cc b/gcc/builtins.cc
index b9d89b409b8..22269318e8c 100644
--- a/gcc/builtins.cc
+++ b/gcc/builtins.cc
@@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "demangle.h"
 #include "gimple-range.h"
 #include "pointer-query.h"
+#include "opts.h"
 
 struct target_builtins default_target_builtins;
 #if SWITCHABLE_TARGET
@@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
 	return target;
       if (fcode == BUILT_IN_MEMCMP_EQ)
 	{
-	  tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
+	  tree newdecl = builtin_decl_explicit
+	    (extra_libc_functions.has_memcmpeq
+	     ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
 	  TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
 	}
       break;
diff --git a/gcc/builtins.def b/gcc/builtins.def
index 005976f34e9..eb8d33b16e9 100644
--- a/gcc/builtins.def
+++ b/gcc/builtins.def
@@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
    equality with zero.  */
 DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
 
+/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
+   -fextra-libc-function=memcmpeq.  */
+DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
+
 /* An internal version of strcmp/strncmp, used when the result is only 
    tested for equality with zero.  */
 DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
diff --git a/gcc/common.opt b/gcc/common.opt
index 7ca0cceed82..7a7631682b0 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
 EnumValue
 Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
 
+fextra-libc-function=
+Common Driver Joined
+Specify the extra function in the C library.
+
 ; Whether we permit the extended set of values for FLT_EVAL_METHOD
 ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
 fpermitted-flt-eval-methods=
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 8cd5bdddc5d..fe1e3709953 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
 -ffixed-@var{reg}  -fexceptions @gol
 -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
 -fasynchronous-unwind-tables @gol
+-fextra-libc-function=memcmpeq @gol
 -fno-gnu-unique @gol
 -finhibit-size-directive  -fcommon  -fno-ident @gol
 -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
@@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
 table is exact at each instruction boundary, so it can be used for stack
 unwinding from asynchronous events (such as debugger or garbage collector).
 
+@item -fextra-libc-function=memcmpeq
+@opindex fextra-libc-function
+Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
+@code{__builtin_memcmp_eq}.
+
 @item -fno-gnu-unique
 @opindex fno-gnu-unique
 @opindex fgnu-unique
diff --git a/gcc/opts.cc b/gcc/opts.cc
index bf06a55456a..e77f0922acc 100644
--- a/gcc/opts.cc
+++ b/gcc/opts.cc
@@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
 /* In this file all option sets are explicit.  */
 #undef OPTION_SET_P
 
+/* The list of extra functions in the C library.  */
+extra_libc_function_list extra_libc_functions;
+
 static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
 
 /* Names of fundamental debug info formats indexed by enum
@@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
   return flags;
 }
 
+/* Parse -fextra-libc-function= suboptions from ARG.  */
+
+static void
+parse_extra_libc_function (const char *arg)
+{
+  /* Check to see if the string matches a sub-option name.  */
+  if (strcmp (arg, "memcmpeq") == 0)
+    {
+      extra_libc_functions.has_memcmpeq = 1;
+      return;
+    }
+
+  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
+	 arg);
+}
+
 /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
 
 unsigned int
@@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
       break;
 
+    case OPT_fextra_libc_function_:
+      parse_extra_libc_function (arg);
+      break;
+
     case OPT_fprofile_generate_:
       opts->x_profile_data_prefix = xstrdup (arg);
       value = true;
diff --git a/gcc/opts.h b/gcc/opts.h
index a43ce66cffe..e8d8835ba23 100644
--- a/gcc/opts.h
+++ b/gcc/opts.h
@@ -345,6 +345,13 @@ struct cl_option_handlers
 extern const char *opt_fstack_limit_symbol_arg;
 extern int opt_fstack_limit_register_no;
 
+/* The list of extra functions in the C library.  */
+struct extra_libc_function_list
+{
+  unsigned int has_memcmpeq : 1;
+};
+extern extra_libc_function_list extra_libc_functions;
+
 /* Input file names.  */
 
 extern const char **in_fnames;
diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
new file mode 100644
index 00000000000..487f6cd98db
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
+/* { dg-final { scan-assembler "__memcmpeq" } } */
+
+#include <stddef.h>
+
+int
+foo (const char *s1, const char *s2, size_t len)
+{
+  return __builtin_memcmp (s1, s2, len) != 0;
+}
diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
new file mode 100644
index 00000000000..1773dc2bee1
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
+/* { dg-final { scan-assembler "__memcmpeq" } } */
+
+#include <string.h>
+
+int
+foo (const char *s1, const char *s2, size_t len)
+{
+  return memcmp (s1, s2, len) == 0;
+}
diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
new file mode 100644
index 00000000000..69c9537d572
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
+/* { dg-final { scan-assembler-not "__memcmpeq" } } */
+
+#include <string.h>
+
+int
+foo (const char *s1, const char *s2, size_t len)
+{
+  return memcmp (s1, s2, len);
+}
diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
new file mode 100644
index 00000000000..a448312ea96
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler-not "__memcmpeq" } } */
+
+#include <stddef.h>
+
+int
+foo (const char *s1, const char *s2, size_t len)
+{
+  return __builtin_memcmp (s1, s2, len) != 0;
+}
diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
new file mode 100644
index 00000000000..4ef33a1c238
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler-not "__memcmpeq" } } */
+
+#include <string.h>
+
+int
+foo (const char *s1, const char *s2, size_t len)
+{
+  return memcmp (s1, s2, len) == 0;
+}
diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
new file mode 100644
index 00000000000..52304df7079
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
+/* { dg-final { scan-assembler "__memcmpeq" } } */
+
+#include <stddef.h>
+
+int
+foo (const char *s1, const char *s2, size_t len)
+{
+  return __builtin_memcmp_eq (s1, s2, len) != 0;
+}
diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
new file mode 100644
index 00000000000..d59765894e7
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler-not "__memcmpeq" } } */
+
+#include <stddef.h>
+
+int
+foo (const char *s1, const char *s2, size_t len)
+{
+  return __builtin_memcmp_eq (s1, s2, len) != 0;
+}
-- 
2.36.1

Re: [PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[Richard Biener]

On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Add -fextra-libc-function=memcmpeq to map
>
> extern int __memcmpeq (const void *, const void *, size_t);
>
> which was added to GLIBC 2.35, to __builtin_memcmp_eq.

Humm.  Can't we instead use the presence of a declaration
of __memcmpeq with a GNU standard dialect as this instead of
adding a weird -fextra-libc-function= option?  Maybe that's even
reasonable with a non-GNU dialect standard in effect since
__ prefixed names are in the implementation namespace?

Richard.

> gcc/
>
>         * builtins.cc: Include "opts.h".
>         (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
>         available.
>         * builtins.def (BUILT_IN___MEMCMPEQ): New.
>         * common.opt: Add -fextra-libc-function=.
>         * opts.cc (extra_libc_functions): New.
>         (parse_extra_libc_function): New function.
>         (common_handle_option): Handle -fextra-libc-function=.
>         * opts.h (extra_libc_function_list): New.
>         (extra_libc_functions): Likewise.
>         * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
>
> gcc/testsuite/
>
>         * c-c++-common/memcmpeq-1.c: New test.
>         * c-c++-common/memcmpeq-2.c: Likewise.
>         * c-c++-common/memcmpeq-3.c: Likewise.
>         * c-c++-common/memcmpeq-4.c: Likewise.
>         * c-c++-common/memcmpeq-5.c: Likewise.
>         * c-c++-common/memcmpeq-6.c: Likewise.
>         * c-c++-common/memcmpeq-7.c: Likewise.
> ---
>  gcc/builtins.cc                         |  5 ++++-
>  gcc/builtins.def                        |  4 ++++
>  gcc/common.opt                          |  4 ++++
>  gcc/doc/invoke.texi                     |  6 ++++++
>  gcc/opts.cc                             | 23 +++++++++++++++++++++++
>  gcc/opts.h                              |  7 +++++++
>  gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
>  13 files changed, 125 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
>
> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> index b9d89b409b8..22269318e8c 100644
> --- a/gcc/builtins.cc
> +++ b/gcc/builtins.cc
> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "demangle.h"
>  #include "gimple-range.h"
>  #include "pointer-query.h"
> +#include "opts.h"
>
>  struct target_builtins default_target_builtins;
>  #if SWITCHABLE_TARGET
> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
>         return target;
>        if (fcode == BUILT_IN_MEMCMP_EQ)
>         {
> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> +         tree newdecl = builtin_decl_explicit
> +           (extra_libc_functions.has_memcmpeq
> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
>           TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
>         }
>        break;
> diff --git a/gcc/builtins.def b/gcc/builtins.def
> index 005976f34e9..eb8d33b16e9 100644
> --- a/gcc/builtins.def
> +++ b/gcc/builtins.def
> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
>     equality with zero.  */
>  DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
>
> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> +   -fextra-libc-function=memcmpeq.  */
> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> +
>  /* An internal version of strcmp/strncmp, used when the result is only
>     tested for equality with zero.  */
>  DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> diff --git a/gcc/common.opt b/gcc/common.opt
> index 7ca0cceed82..7a7631682b0 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
>  EnumValue
>  Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
>
> +fextra-libc-function=
> +Common Driver Joined
> +Specify the extra function in the C library.
> +
>  ; Whether we permit the extended set of values for FLT_EVAL_METHOD
>  ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
>  fpermitted-flt-eval-methods=
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 8cd5bdddc5d..fe1e3709953 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
>  -ffixed-@var{reg}  -fexceptions @gol
>  -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
>  -fasynchronous-unwind-tables @gol
> +-fextra-libc-function=memcmpeq @gol
>  -fno-gnu-unique @gol
>  -finhibit-size-directive  -fcommon  -fno-ident @gol
>  -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
>  table is exact at each instruction boundary, so it can be used for stack
>  unwinding from asynchronous events (such as debugger or garbage collector).
>
> +@item -fextra-libc-function=memcmpeq
> +@opindex fextra-libc-function
> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> +@code{__builtin_memcmp_eq}.
> +
>  @item -fno-gnu-unique
>  @opindex fno-gnu-unique
>  @opindex fgnu-unique
> diff --git a/gcc/opts.cc b/gcc/opts.cc
> index bf06a55456a..e77f0922acc 100644
> --- a/gcc/opts.cc
> +++ b/gcc/opts.cc
> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
>  /* In this file all option sets are explicit.  */
>  #undef OPTION_SET_P
>
> +/* The list of extra functions in the C library.  */
> +extra_libc_function_list extra_libc_functions;
> +
>  static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
>
>  /* Names of fundamental debug info formats indexed by enum
> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
>    return flags;
>  }
>
> +/* Parse -fextra-libc-function= suboptions from ARG.  */
> +
> +static void
> +parse_extra_libc_function (const char *arg)
> +{
> +  /* Check to see if the string matches a sub-option name.  */
> +  if (strcmp (arg, "memcmpeq") == 0)
> +    {
> +      extra_libc_functions.has_memcmpeq = 1;
> +      return;
> +    }
> +
> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> +        arg);
> +}
> +
>  /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
>
>  unsigned int
> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
>        SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
>        break;
>
> +    case OPT_fextra_libc_function_:
> +      parse_extra_libc_function (arg);
> +      break;
> +
>      case OPT_fprofile_generate_:
>        opts->x_profile_data_prefix = xstrdup (arg);
>        value = true;
> diff --git a/gcc/opts.h b/gcc/opts.h
> index a43ce66cffe..e8d8835ba23 100644
> --- a/gcc/opts.h
> +++ b/gcc/opts.h
> @@ -345,6 +345,13 @@ struct cl_option_handlers
>  extern const char *opt_fstack_limit_symbol_arg;
>  extern int opt_fstack_limit_register_no;
>
> +/* The list of extra functions in the C library.  */
> +struct extra_libc_function_list
> +{
> +  unsigned int has_memcmpeq : 1;
> +};
> +extern extra_libc_function_list extra_libc_functions;
> +
>  /* Input file names.  */
>
>  extern const char **in_fnames;
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> new file mode 100644
> index 00000000000..487f6cd98db
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin_memcmp (s1, s2, len) != 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> new file mode 100644
> index 00000000000..1773dc2bee1
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> +
> +#include <string.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return memcmp (s1, s2, len) == 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> new file mode 100644
> index 00000000000..69c9537d572
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include <string.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return memcmp (s1, s2, len);
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> new file mode 100644
> index 00000000000..a448312ea96
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin_memcmp (s1, s2, len) != 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> new file mode 100644
> index 00000000000..4ef33a1c238
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include <string.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return memcmp (s1, s2, len) == 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> new file mode 100644
> index 00000000000..52304df7079
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> new file mode 100644
> index 00000000000..d59765894e7
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> +}
> --
> 2.36.1
>

Re: [PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[H.J. Lu]

On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Add -fextra-libc-function=memcmpeq to map
> >
> > extern int __memcmpeq (const void *, const void *, size_t);
> >
> > which was added to GLIBC 2.35, to __builtin_memcmp_eq.
>
> Humm.  Can't we instead use the presence of a declaration
> of __memcmpeq with a GNU standard dialect as this instead of
> adding a weird -fextra-libc-function= option?  Maybe that's even
> reasonable with a non-GNU dialect standard in effect since
> __ prefixed names are in the implementation namespace?

But not all source codes include <string.h> and GCC may generate
memcmp directly.  How should we handle these cases?

> Richard.
>
> > gcc/
> >
> >         * builtins.cc: Include "opts.h".
> >         (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
> >         available.
> >         * builtins.def (BUILT_IN___MEMCMPEQ): New.
> >         * common.opt: Add -fextra-libc-function=.
> >         * opts.cc (extra_libc_functions): New.
> >         (parse_extra_libc_function): New function.
> >         (common_handle_option): Handle -fextra-libc-function=.
> >         * opts.h (extra_libc_function_list): New.
> >         (extra_libc_functions): Likewise.
> >         * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
> >
> > gcc/testsuite/
> >
> >         * c-c++-common/memcmpeq-1.c: New test.
> >         * c-c++-common/memcmpeq-2.c: Likewise.
> >         * c-c++-common/memcmpeq-3.c: Likewise.
> >         * c-c++-common/memcmpeq-4.c: Likewise.
> >         * c-c++-common/memcmpeq-5.c: Likewise.
> >         * c-c++-common/memcmpeq-6.c: Likewise.
> >         * c-c++-common/memcmpeq-7.c: Likewise.
> > ---
> >  gcc/builtins.cc                         |  5 ++++-
> >  gcc/builtins.def                        |  4 ++++
> >  gcc/common.opt                          |  4 ++++
> >  gcc/doc/invoke.texi                     |  6 ++++++
> >  gcc/opts.cc                             | 23 +++++++++++++++++++++++
> >  gcc/opts.h                              |  7 +++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
> >  13 files changed, 125 insertions(+), 1 deletion(-)
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
> >
> > diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> > index b9d89b409b8..22269318e8c 100644
> > --- a/gcc/builtins.cc
> > +++ b/gcc/builtins.cc
> > @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
> >  #include "demangle.h"
> >  #include "gimple-range.h"
> >  #include "pointer-query.h"
> > +#include "opts.h"
> >
> >  struct target_builtins default_target_builtins;
> >  #if SWITCHABLE_TARGET
> > @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
> >         return target;
> >        if (fcode == BUILT_IN_MEMCMP_EQ)
> >         {
> > -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> > +         tree newdecl = builtin_decl_explicit
> > +           (extra_libc_functions.has_memcmpeq
> > +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
> >           TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
> >         }
> >        break;
> > diff --git a/gcc/builtins.def b/gcc/builtins.def
> > index 005976f34e9..eb8d33b16e9 100644
> > --- a/gcc/builtins.def
> > +++ b/gcc/builtins.def
> > @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
> >     equality with zero.  */
> >  DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
> >
> > +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> > +   -fextra-libc-function=memcmpeq.  */
> > +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> > +
> >  /* An internal version of strcmp/strncmp, used when the result is only
> >     tested for equality with zero.  */
> >  DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> > diff --git a/gcc/common.opt b/gcc/common.opt
> > index 7ca0cceed82..7a7631682b0 100644
> > --- a/gcc/common.opt
> > +++ b/gcc/common.opt
> > @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
> >  EnumValue
> >  Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
> >
> > +fextra-libc-function=
> > +Common Driver Joined
> > +Specify the extra function in the C library.
> > +
> >  ; Whether we permit the extended set of values for FLT_EVAL_METHOD
> >  ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
> >  fpermitted-flt-eval-methods=
> > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > index 8cd5bdddc5d..fe1e3709953 100644
> > --- a/gcc/doc/invoke.texi
> > +++ b/gcc/doc/invoke.texi
> > @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
> >  -ffixed-@var{reg}  -fexceptions @gol
> >  -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
> >  -fasynchronous-unwind-tables @gol
> > +-fextra-libc-function=memcmpeq @gol
> >  -fno-gnu-unique @gol
> >  -finhibit-size-directive  -fcommon  -fno-ident @gol
> >  -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> > @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
> >  table is exact at each instruction boundary, so it can be used for stack
> >  unwinding from asynchronous events (such as debugger or garbage collector).
> >
> > +@item -fextra-libc-function=memcmpeq
> > +@opindex fextra-libc-function
> > +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> > +@code{__builtin_memcmp_eq}.
> > +
> >  @item -fno-gnu-unique
> >  @opindex fno-gnu-unique
> >  @opindex fgnu-unique
> > diff --git a/gcc/opts.cc b/gcc/opts.cc
> > index bf06a55456a..e77f0922acc 100644
> > --- a/gcc/opts.cc
> > +++ b/gcc/opts.cc
> > @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
> >  /* In this file all option sets are explicit.  */
> >  #undef OPTION_SET_P
> >
> > +/* The list of extra functions in the C library.  */
> > +extra_libc_function_list extra_libc_functions;
> > +
> >  static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
> >
> >  /* Names of fundamental debug info formats indexed by enum
> > @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
> >    return flags;
> >  }
> >
> > +/* Parse -fextra-libc-function= suboptions from ARG.  */
> > +
> > +static void
> > +parse_extra_libc_function (const char *arg)
> > +{
> > +  /* Check to see if the string matches a sub-option name.  */
> > +  if (strcmp (arg, "memcmpeq") == 0)
> > +    {
> > +      extra_libc_functions.has_memcmpeq = 1;
> > +      return;
> > +    }
> > +
> > +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> > +        arg);
> > +}
> > +
> >  /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
> >
> >  unsigned int
> > @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
> >        SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
> >        break;
> >
> > +    case OPT_fextra_libc_function_:
> > +      parse_extra_libc_function (arg);
> > +      break;
> > +
> >      case OPT_fprofile_generate_:
> >        opts->x_profile_data_prefix = xstrdup (arg);
> >        value = true;
> > diff --git a/gcc/opts.h b/gcc/opts.h
> > index a43ce66cffe..e8d8835ba23 100644
> > --- a/gcc/opts.h
> > +++ b/gcc/opts.h
> > @@ -345,6 +345,13 @@ struct cl_option_handlers
> >  extern const char *opt_fstack_limit_symbol_arg;
> >  extern int opt_fstack_limit_register_no;
> >
> > +/* The list of extra functions in the C library.  */
> > +struct extra_libc_function_list
> > +{
> > +  unsigned int has_memcmpeq : 1;
> > +};
> > +extern extra_libc_function_list extra_libc_functions;
> > +
> >  /* Input file names.  */
> >
> >  extern const char **in_fnames;
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > new file mode 100644
> > index 00000000000..487f6cd98db
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > +
> > +#include <stddef.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return __builtin_memcmp (s1, s2, len) != 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > new file mode 100644
> > index 00000000000..1773dc2bee1
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > +
> > +#include <string.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return memcmp (s1, s2, len) == 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > new file mode 100644
> > index 00000000000..69c9537d572
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > +
> > +#include <string.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return memcmp (s1, s2, len);
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > new file mode 100644
> > index 00000000000..a448312ea96
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > +
> > +#include <stddef.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return __builtin_memcmp (s1, s2, len) != 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > new file mode 100644
> > index 00000000000..4ef33a1c238
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > +
> > +#include <string.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return memcmp (s1, s2, len) == 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > new file mode 100644
> > index 00000000000..52304df7079
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > +
> > +#include <stddef.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > new file mode 100644
> > index 00000000000..d59765894e7
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > +
> > +#include <stddef.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > +}
> > --
> > 2.36.1
> >



-- 
H.J.

Re: [PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[Richard Biener]

> Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> 
> On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> <richard.guenther@gmail.com> wrote:
>> 
>>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
>>> <gcc-patches@gcc.gnu.org> wrote:
>>> 
>>> Add -fextra-libc-function=memcmpeq to map
>>> 
>>> extern int __memcmpeq (const void *, const void *, size_t);
>>> 
>>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
>> 
>> Humm.  Can't we instead use the presence of a declaration
>> of __memcmpeq with a GNU standard dialect as this instead of
>> adding a weird -fextra-libc-function= option?  Maybe that's even
>> reasonable with a non-GNU dialect standard in effect since
>> __ prefixed names are in the implementation namespace?
> 
> But not all source codes include <string.h> and GCC may generate
> memcmp directly.  How should we handle these cases?

Not.  Similar as to vectorized math functions.
I think it’s not worth optimizing for this case.

Richard.

> 
>> Richard.
>> 
>>> gcc/
>>> 
>>>        * builtins.cc: Include "opts.h".
>>>        (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
>>>        available.
>>>        * builtins.def (BUILT_IN___MEMCMPEQ): New.
>>>        * common.opt: Add -fextra-libc-function=.
>>>        * opts.cc (extra_libc_functions): New.
>>>        (parse_extra_libc_function): New function.
>>>        (common_handle_option): Handle -fextra-libc-function=.
>>>        * opts.h (extra_libc_function_list): New.
>>>        (extra_libc_functions): Likewise.
>>>        * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
>>> 
>>> gcc/testsuite/
>>> 
>>>        * c-c++-common/memcmpeq-1.c: New test.
>>>        * c-c++-common/memcmpeq-2.c: Likewise.
>>>        * c-c++-common/memcmpeq-3.c: Likewise.
>>>        * c-c++-common/memcmpeq-4.c: Likewise.
>>>        * c-c++-common/memcmpeq-5.c: Likewise.
>>>        * c-c++-common/memcmpeq-6.c: Likewise.
>>>        * c-c++-common/memcmpeq-7.c: Likewise.
>>> ---
>>> gcc/builtins.cc                         |  5 ++++-
>>> gcc/builtins.def                        |  4 ++++
>>> gcc/common.opt                          |  4 ++++
>>> gcc/doc/invoke.texi                     |  6 ++++++
>>> gcc/opts.cc                             | 23 +++++++++++++++++++++++
>>> gcc/opts.h                              |  7 +++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
>>> 13 files changed, 125 insertions(+), 1 deletion(-)
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
>>> 
>>> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
>>> index b9d89b409b8..22269318e8c 100644
>>> --- a/gcc/builtins.cc
>>> +++ b/gcc/builtins.cc
>>> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
>>> #include "demangle.h"
>>> #include "gimple-range.h"
>>> #include "pointer-query.h"
>>> +#include "opts.h"
>>> 
>>> struct target_builtins default_target_builtins;
>>> #if SWITCHABLE_TARGET
>>> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
>>>        return target;
>>>       if (fcode == BUILT_IN_MEMCMP_EQ)
>>>        {
>>> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
>>> +         tree newdecl = builtin_decl_explicit
>>> +           (extra_libc_functions.has_memcmpeq
>>> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
>>>          TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
>>>        }
>>>       break;
>>> diff --git a/gcc/builtins.def b/gcc/builtins.def
>>> index 005976f34e9..eb8d33b16e9 100644
>>> --- a/gcc/builtins.def
>>> +++ b/gcc/builtins.def
>>> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
>>>    equality with zero.  */
>>> DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
>>> 
>>> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
>>> +   -fextra-libc-function=memcmpeq.  */
>>> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
>>> +
>>> /* An internal version of strcmp/strncmp, used when the result is only
>>>    tested for equality with zero.  */
>>> DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
>>> diff --git a/gcc/common.opt b/gcc/common.opt
>>> index 7ca0cceed82..7a7631682b0 100644
>>> --- a/gcc/common.opt
>>> +++ b/gcc/common.opt
>>> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
>>> EnumValue
>>> Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
>>> 
>>> +fextra-libc-function=
>>> +Common Driver Joined
>>> +Specify the extra function in the C library.
>>> +
>>> ; Whether we permit the extended set of values for FLT_EVAL_METHOD
>>> ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
>>> fpermitted-flt-eval-methods=
>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>> index 8cd5bdddc5d..fe1e3709953 100644
>>> --- a/gcc/doc/invoke.texi
>>> +++ b/gcc/doc/invoke.texi
>>> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
>>> -ffixed-@var{reg}  -fexceptions @gol
>>> -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
>>> -fasynchronous-unwind-tables @gol
>>> +-fextra-libc-function=memcmpeq @gol
>>> -fno-gnu-unique @gol
>>> -finhibit-size-directive  -fcommon  -fno-ident @gol
>>> -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
>>> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
>>> table is exact at each instruction boundary, so it can be used for stack
>>> unwinding from asynchronous events (such as debugger or garbage collector).
>>> 
>>> +@item -fextra-libc-function=memcmpeq
>>> +@opindex fextra-libc-function
>>> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
>>> +@code{__builtin_memcmp_eq}.
>>> +
>>> @item -fno-gnu-unique
>>> @opindex fno-gnu-unique
>>> @opindex fgnu-unique
>>> diff --git a/gcc/opts.cc b/gcc/opts.cc
>>> index bf06a55456a..e77f0922acc 100644
>>> --- a/gcc/opts.cc
>>> +++ b/gcc/opts.cc
>>> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
>>> /* In this file all option sets are explicit.  */
>>> #undef OPTION_SET_P
>>> 
>>> +/* The list of extra functions in the C library.  */
>>> +extra_libc_function_list extra_libc_functions;
>>> +
>>> static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
>>> 
>>> /* Names of fundamental debug info formats indexed by enum
>>> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
>>>   return flags;
>>> }
>>> 
>>> +/* Parse -fextra-libc-function= suboptions from ARG.  */
>>> +
>>> +static void
>>> +parse_extra_libc_function (const char *arg)
>>> +{
>>> +  /* Check to see if the string matches a sub-option name.  */
>>> +  if (strcmp (arg, "memcmpeq") == 0)
>>> +    {
>>> +      extra_libc_functions.has_memcmpeq = 1;
>>> +      return;
>>> +    }
>>> +
>>> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
>>> +        arg);
>>> +}
>>> +
>>> /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
>>> 
>>> unsigned int
>>> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
>>>       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
>>>       break;
>>> 
>>> +    case OPT_fextra_libc_function_:
>>> +      parse_extra_libc_function (arg);
>>> +      break;
>>> +
>>>     case OPT_fprofile_generate_:
>>>       opts->x_profile_data_prefix = xstrdup (arg);
>>>       value = true;
>>> diff --git a/gcc/opts.h b/gcc/opts.h
>>> index a43ce66cffe..e8d8835ba23 100644
>>> --- a/gcc/opts.h
>>> +++ b/gcc/opts.h
>>> @@ -345,6 +345,13 @@ struct cl_option_handlers
>>> extern const char *opt_fstack_limit_symbol_arg;
>>> extern int opt_fstack_limit_register_no;
>>> 
>>> +/* The list of extra functions in the C library.  */
>>> +struct extra_libc_function_list
>>> +{
>>> +  unsigned int has_memcmpeq : 1;
>>> +};
>>> +extern extra_libc_function_list extra_libc_functions;
>>> +
>>> /* Input file names.  */
>>> 
>>> extern const char **in_fnames;
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
>>> new file mode 100644
>>> index 00000000000..487f6cd98db
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
>>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return __builtin_memcmp (s1, s2, len) != 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
>>> new file mode 100644
>>> index 00000000000..1773dc2bee1
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
>>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
>>> +
>>> +#include <string.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return memcmp (s1, s2, len) == 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
>>> new file mode 100644
>>> index 00000000000..69c9537d572
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
>>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
>>> +
>>> +#include <string.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return memcmp (s1, s2, len);
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
>>> new file mode 100644
>>> index 00000000000..a448312ea96
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2" } */
>>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return __builtin_memcmp (s1, s2, len) != 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
>>> new file mode 100644
>>> index 00000000000..4ef33a1c238
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2" } */
>>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
>>> +
>>> +#include <string.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return memcmp (s1, s2, len) == 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
>>> new file mode 100644
>>> index 00000000000..52304df7079
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
>>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
>>> new file mode 100644
>>> index 00000000000..d59765894e7
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2" } */
>>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
>>> +}
>>> --
>>> 2.36.1
>>> 
> 
> 
> 
> -- 
> H.J.

Re: [PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[H.J. Lu]

On Mon, Jun 13, 2022 at 9:01 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
>
>
> > Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> >
> > On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> > <richard.guenther@gmail.com> wrote:
> >>
> >>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> >>> <gcc-patches@gcc.gnu.org> wrote:
> >>>
> >>> Add -fextra-libc-function=memcmpeq to map
> >>>
> >>> extern int __memcmpeq (const void *, const void *, size_t);
> >>>
> >>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
> >>
> >> Humm.  Can't we instead use the presence of a declaration
> >> of __memcmpeq with a GNU standard dialect as this instead of
> >> adding a weird -fextra-libc-function= option?  Maybe that's even
> >> reasonable with a non-GNU dialect standard in effect since
> >> __ prefixed names are in the implementation namespace?
> >
> > But not all source codes include <string.h> and GCC may generate
> > memcmp directly.  How should we handle these cases?
>
> Not.  Similar as to vectorized math functions.
> I think it’s not worth optimizing for this case.

Another question.  Should we consider any __memcmpeq prototype
or just the one in the system header file?

> Richard.
>
> >
> >> Richard.
> >>
> >>> gcc/
> >>>
> >>>        * builtins.cc: Include "opts.h".
> >>>        (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
> >>>        available.
> >>>        * builtins.def (BUILT_IN___MEMCMPEQ): New.
> >>>        * common.opt: Add -fextra-libc-function=.
> >>>        * opts.cc (extra_libc_functions): New.
> >>>        (parse_extra_libc_function): New function.
> >>>        (common_handle_option): Handle -fextra-libc-function=.
> >>>        * opts.h (extra_libc_function_list): New.
> >>>        (extra_libc_functions): Likewise.
> >>>        * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
> >>>
> >>> gcc/testsuite/
> >>>
> >>>        * c-c++-common/memcmpeq-1.c: New test.
> >>>        * c-c++-common/memcmpeq-2.c: Likewise.
> >>>        * c-c++-common/memcmpeq-3.c: Likewise.
> >>>        * c-c++-common/memcmpeq-4.c: Likewise.
> >>>        * c-c++-common/memcmpeq-5.c: Likewise.
> >>>        * c-c++-common/memcmpeq-6.c: Likewise.
> >>>        * c-c++-common/memcmpeq-7.c: Likewise.
> >>> ---
> >>> gcc/builtins.cc                         |  5 ++++-
> >>> gcc/builtins.def                        |  4 ++++
> >>> gcc/common.opt                          |  4 ++++
> >>> gcc/doc/invoke.texi                     |  6 ++++++
> >>> gcc/opts.cc                             | 23 +++++++++++++++++++++++
> >>> gcc/opts.h                              |  7 +++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
> >>> 13 files changed, 125 insertions(+), 1 deletion(-)
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
> >>>
> >>> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> >>> index b9d89b409b8..22269318e8c 100644
> >>> --- a/gcc/builtins.cc
> >>> +++ b/gcc/builtins.cc
> >>> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
> >>> #include "demangle.h"
> >>> #include "gimple-range.h"
> >>> #include "pointer-query.h"
> >>> +#include "opts.h"
> >>>
> >>> struct target_builtins default_target_builtins;
> >>> #if SWITCHABLE_TARGET
> >>> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
> >>>        return target;
> >>>       if (fcode == BUILT_IN_MEMCMP_EQ)
> >>>        {
> >>> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> >>> +         tree newdecl = builtin_decl_explicit
> >>> +           (extra_libc_functions.has_memcmpeq
> >>> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
> >>>          TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
> >>>        }
> >>>       break;
> >>> diff --git a/gcc/builtins.def b/gcc/builtins.def
> >>> index 005976f34e9..eb8d33b16e9 100644
> >>> --- a/gcc/builtins.def
> >>> +++ b/gcc/builtins.def
> >>> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
> >>>    equality with zero.  */
> >>> DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
> >>>
> >>> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> >>> +   -fextra-libc-function=memcmpeq.  */
> >>> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> >>> +
> >>> /* An internal version of strcmp/strncmp, used when the result is only
> >>>    tested for equality with zero.  */
> >>> DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> >>> diff --git a/gcc/common.opt b/gcc/common.opt
> >>> index 7ca0cceed82..7a7631682b0 100644
> >>> --- a/gcc/common.opt
> >>> +++ b/gcc/common.opt
> >>> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
> >>> EnumValue
> >>> Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
> >>>
> >>> +fextra-libc-function=
> >>> +Common Driver Joined
> >>> +Specify the extra function in the C library.
> >>> +
> >>> ; Whether we permit the extended set of values for FLT_EVAL_METHOD
> >>> ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
> >>> fpermitted-flt-eval-methods=
> >>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> >>> index 8cd5bdddc5d..fe1e3709953 100644
> >>> --- a/gcc/doc/invoke.texi
> >>> +++ b/gcc/doc/invoke.texi
> >>> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
> >>> -ffixed-@var{reg}  -fexceptions @gol
> >>> -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
> >>> -fasynchronous-unwind-tables @gol
> >>> +-fextra-libc-function=memcmpeq @gol
> >>> -fno-gnu-unique @gol
> >>> -finhibit-size-directive  -fcommon  -fno-ident @gol
> >>> -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> >>> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
> >>> table is exact at each instruction boundary, so it can be used for stack
> >>> unwinding from asynchronous events (such as debugger or garbage collector).
> >>>
> >>> +@item -fextra-libc-function=memcmpeq
> >>> +@opindex fextra-libc-function
> >>> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> >>> +@code{__builtin_memcmp_eq}.
> >>> +
> >>> @item -fno-gnu-unique
> >>> @opindex fno-gnu-unique
> >>> @opindex fgnu-unique
> >>> diff --git a/gcc/opts.cc b/gcc/opts.cc
> >>> index bf06a55456a..e77f0922acc 100644
> >>> --- a/gcc/opts.cc
> >>> +++ b/gcc/opts.cc
> >>> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
> >>> /* In this file all option sets are explicit.  */
> >>> #undef OPTION_SET_P
> >>>
> >>> +/* The list of extra functions in the C library.  */
> >>> +extra_libc_function_list extra_libc_functions;
> >>> +
> >>> static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
> >>>
> >>> /* Names of fundamental debug info formats indexed by enum
> >>> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
> >>>   return flags;
> >>> }
> >>>
> >>> +/* Parse -fextra-libc-function= suboptions from ARG.  */
> >>> +
> >>> +static void
> >>> +parse_extra_libc_function (const char *arg)
> >>> +{
> >>> +  /* Check to see if the string matches a sub-option name.  */
> >>> +  if (strcmp (arg, "memcmpeq") == 0)
> >>> +    {
> >>> +      extra_libc_functions.has_memcmpeq = 1;
> >>> +      return;
> >>> +    }
> >>> +
> >>> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> >>> +        arg);
> >>> +}
> >>> +
> >>> /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
> >>>
> >>> unsigned int
> >>> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
> >>>       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
> >>>       break;
> >>>
> >>> +    case OPT_fextra_libc_function_:
> >>> +      parse_extra_libc_function (arg);
> >>> +      break;
> >>> +
> >>>     case OPT_fprofile_generate_:
> >>>       opts->x_profile_data_prefix = xstrdup (arg);
> >>>       value = true;
> >>> diff --git a/gcc/opts.h b/gcc/opts.h
> >>> index a43ce66cffe..e8d8835ba23 100644
> >>> --- a/gcc/opts.h
> >>> +++ b/gcc/opts.h
> >>> @@ -345,6 +345,13 @@ struct cl_option_handlers
> >>> extern const char *opt_fstack_limit_symbol_arg;
> >>> extern int opt_fstack_limit_register_no;
> >>>
> >>> +/* The list of extra functions in the C library.  */
> >>> +struct extra_libc_function_list
> >>> +{
> >>> +  unsigned int has_memcmpeq : 1;
> >>> +};
> >>> +extern extra_libc_function_list extra_libc_functions;
> >>> +
> >>> /* Input file names.  */
> >>>
> >>> extern const char **in_fnames;
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> >>> new file mode 100644
> >>> index 00000000000..487f6cd98db
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> >>> +
> >>> +#include <stddef.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> >>> new file mode 100644
> >>> index 00000000000..1773dc2bee1
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> >>> +
> >>> +#include <string.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return memcmp (s1, s2, len) == 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> >>> new file mode 100644
> >>> index 00000000000..69c9537d572
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> >>> +
> >>> +#include <string.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return memcmp (s1, s2, len);
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> >>> new file mode 100644
> >>> index 00000000000..a448312ea96
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2" } */
> >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> >>> +
> >>> +#include <stddef.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> >>> new file mode 100644
> >>> index 00000000000..4ef33a1c238
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2" } */
> >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> >>> +
> >>> +#include <string.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return memcmp (s1, s2, len) == 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> >>> new file mode 100644
> >>> index 00000000000..52304df7079
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> >>> +
> >>> +#include <stddef.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> >>> new file mode 100644
> >>> index 00000000000..d59765894e7
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2" } */
> >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> >>> +
> >>> +#include <stddef.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> >>> +}
> >>> --
> >>> 2.36.1
> >>>
> >
> >
> >
> > --
> > H.J.



-- 
H.J.

Re: [PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[Fangrui Song]

On Wed, Jun 15, 2022 at 2:44 PM H.J. Lu via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Mon, Jun 13, 2022 at 9:01 AM Richard Biener
> <richard.guenther@gmail.com> wrote:
> >
> >
> >
> > > Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> > >
> > > On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> > > <richard.guenther@gmail.com> wrote:
> > >>
> > >>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> > >>> <gcc-patches@gcc.gnu.org> wrote:
> > >>>
> > >>> Add -fextra-libc-function=memcmpeq to map
> > >>>
> > >>> extern int __memcmpeq (const void *, const void *, size_t);
> > >>>
> > >>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
> > >>
> > >> Humm.  Can't we instead use the presence of a declaration
> > >> of __memcmpeq with a GNU standard dialect as this instead of
> > >> adding a weird -fextra-libc-function= option?  Maybe that's even
> > >> reasonable with a non-GNU dialect standard in effect since
> > >> __ prefixed names are in the implementation namespace?
> > >
> > > But not all source codes include <string.h> and GCC may generate
> > > memcmp directly.  How should we handle these cases?
> >
> > Not.  Similar as to vectorized math functions.
> > I think it’s not worth optimizing for this case.
>
> Another question.  Should we consider any __memcmpeq prototype
> or just the one in the system header file?

An idea from https://reviews.llvm.org/D56593#3586673: -fbuiltin-__memcmpeq

This requires making -fbuiltin-function available, see
https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
("There is no corresponding -fbuiltin-function option")

I prefer an option over a magic behavior about whether a declaration exists.

> > Richard.
> >
> > >
> > >> Richard.
> > >>
> > >>> gcc/
> > >>>
> > >>>        * builtins.cc: Include "opts.h".
> > >>>        (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
> > >>>        available.
> > >>>        * builtins.def (BUILT_IN___MEMCMPEQ): New.
> > >>>        * common.opt: Add -fextra-libc-function=.
> > >>>        * opts.cc (extra_libc_functions): New.
> > >>>        (parse_extra_libc_function): New function.
> > >>>        (common_handle_option): Handle -fextra-libc-function=.
> > >>>        * opts.h (extra_libc_function_list): New.
> > >>>        (extra_libc_functions): Likewise.
> > >>>        * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
> > >>>
> > >>> gcc/testsuite/
> > >>>
> > >>>        * c-c++-common/memcmpeq-1.c: New test.
> > >>>        * c-c++-common/memcmpeq-2.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-3.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-4.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-5.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-6.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-7.c: Likewise.
> > >>> ---
> > >>> gcc/builtins.cc                         |  5 ++++-
> > >>> gcc/builtins.def                        |  4 ++++
> > >>> gcc/common.opt                          |  4 ++++
> > >>> gcc/doc/invoke.texi                     |  6 ++++++
> > >>> gcc/opts.cc                             | 23 +++++++++++++++++++++++
> > >>> gcc/opts.h                              |  7 +++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
> > >>> 13 files changed, 125 insertions(+), 1 deletion(-)
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
> > >>>
> > >>> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> > >>> index b9d89b409b8..22269318e8c 100644
> > >>> --- a/gcc/builtins.cc
> > >>> +++ b/gcc/builtins.cc
> > >>> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
> > >>> #include "demangle.h"
> > >>> #include "gimple-range.h"
> > >>> #include "pointer-query.h"
> > >>> +#include "opts.h"
> > >>>
> > >>> struct target_builtins default_target_builtins;
> > >>> #if SWITCHABLE_TARGET
> > >>> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
> > >>>        return target;
> > >>>       if (fcode == BUILT_IN_MEMCMP_EQ)
> > >>>        {
> > >>> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> > >>> +         tree newdecl = builtin_decl_explicit
> > >>> +           (extra_libc_functions.has_memcmpeq
> > >>> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
> > >>>          TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
> > >>>        }
> > >>>       break;
> > >>> diff --git a/gcc/builtins.def b/gcc/builtins.def
> > >>> index 005976f34e9..eb8d33b16e9 100644
> > >>> --- a/gcc/builtins.def
> > >>> +++ b/gcc/builtins.def
> > >>> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
> > >>>    equality with zero.  */
> > >>> DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
> > >>>
> > >>> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> > >>> +   -fextra-libc-function=memcmpeq.  */
> > >>> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> > >>> +
> > >>> /* An internal version of strcmp/strncmp, used when the result is only
> > >>>    tested for equality with zero.  */
> > >>> DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> > >>> diff --git a/gcc/common.opt b/gcc/common.opt
> > >>> index 7ca0cceed82..7a7631682b0 100644
> > >>> --- a/gcc/common.opt
> > >>> +++ b/gcc/common.opt
> > >>> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
> > >>> EnumValue
> > >>> Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
> > >>>
> > >>> +fextra-libc-function=
> > >>> +Common Driver Joined
> > >>> +Specify the extra function in the C library.
> > >>> +
> > >>> ; Whether we permit the extended set of values for FLT_EVAL_METHOD
> > >>> ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
> > >>> fpermitted-flt-eval-methods=
> > >>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > >>> index 8cd5bdddc5d..fe1e3709953 100644
> > >>> --- a/gcc/doc/invoke.texi
> > >>> +++ b/gcc/doc/invoke.texi
> > >>> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
> > >>> -ffixed-@var{reg}  -fexceptions @gol
> > >>> -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
> > >>> -fasynchronous-unwind-tables @gol
> > >>> +-fextra-libc-function=memcmpeq @gol
> > >>> -fno-gnu-unique @gol
> > >>> -finhibit-size-directive  -fcommon  -fno-ident @gol
> > >>> -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> > >>> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
> > >>> table is exact at each instruction boundary, so it can be used for stack
> > >>> unwinding from asynchronous events (such as debugger or garbage collector).
> > >>>
> > >>> +@item -fextra-libc-function=memcmpeq
> > >>> +@opindex fextra-libc-function
> > >>> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> > >>> +@code{__builtin_memcmp_eq}.
> > >>> +
> > >>> @item -fno-gnu-unique
> > >>> @opindex fno-gnu-unique
> > >>> @opindex fgnu-unique
> > >>> diff --git a/gcc/opts.cc b/gcc/opts.cc
> > >>> index bf06a55456a..e77f0922acc 100644
> > >>> --- a/gcc/opts.cc
> > >>> +++ b/gcc/opts.cc
> > >>> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
> > >>> /* In this file all option sets are explicit.  */
> > >>> #undef OPTION_SET_P
> > >>>
> > >>> +/* The list of extra functions in the C library.  */
> > >>> +extra_libc_function_list extra_libc_functions;
> > >>> +
> > >>> static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
> > >>>
> > >>> /* Names of fundamental debug info formats indexed by enum
> > >>> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
> > >>>   return flags;
> > >>> }
> > >>>
> > >>> +/* Parse -fextra-libc-function= suboptions from ARG.  */
> > >>> +
> > >>> +static void
> > >>> +parse_extra_libc_function (const char *arg)
> > >>> +{
> > >>> +  /* Check to see if the string matches a sub-option name.  */
> > >>> +  if (strcmp (arg, "memcmpeq") == 0)
> > >>> +    {
> > >>> +      extra_libc_functions.has_memcmpeq = 1;
> > >>> +      return;
> > >>> +    }
> > >>> +
> > >>> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> > >>> +        arg);
> > >>> +}
> > >>> +
> > >>> /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
> > >>>
> > >>> unsigned int
> > >>> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
> > >>>       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
> > >>>       break;
> > >>>
> > >>> +    case OPT_fextra_libc_function_:
> > >>> +      parse_extra_libc_function (arg);
> > >>> +      break;
> > >>> +
> > >>>     case OPT_fprofile_generate_:
> > >>>       opts->x_profile_data_prefix = xstrdup (arg);
> > >>>       value = true;
> > >>> diff --git a/gcc/opts.h b/gcc/opts.h
> > >>> index a43ce66cffe..e8d8835ba23 100644
> > >>> --- a/gcc/opts.h
> > >>> +++ b/gcc/opts.h
> > >>> @@ -345,6 +345,13 @@ struct cl_option_handlers
> > >>> extern const char *opt_fstack_limit_symbol_arg;
> > >>> extern int opt_fstack_limit_register_no;
> > >>>
> > >>> +/* The list of extra functions in the C library.  */
> > >>> +struct extra_libc_function_list
> > >>> +{
> > >>> +  unsigned int has_memcmpeq : 1;
> > >>> +};
> > >>> +extern extra_libc_function_list extra_libc_functions;
> > >>> +
> > >>> /* Input file names.  */
> > >>>
> > >>> extern const char **in_fnames;
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > >>> new file mode 100644
> > >>> index 00000000000..487f6cd98db
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > >>> +
> > >>> +#include <stddef.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > >>> new file mode 100644
> > >>> index 00000000000..1773dc2bee1
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > >>> +
> > >>> +#include <string.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return memcmp (s1, s2, len) == 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > >>> new file mode 100644
> > >>> index 00000000000..69c9537d572
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > >>> +
> > >>> +#include <string.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return memcmp (s1, s2, len);
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > >>> new file mode 100644
> > >>> index 00000000000..a448312ea96
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2" } */
> > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > >>> +
> > >>> +#include <stddef.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > >>> new file mode 100644
> > >>> index 00000000000..4ef33a1c238
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2" } */
> > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > >>> +
> > >>> +#include <string.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return memcmp (s1, s2, len) == 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > >>> new file mode 100644
> > >>> index 00000000000..52304df7079
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > >>> +
> > >>> +#include <stddef.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > >>> new file mode 100644
> > >>> index 00000000000..d59765894e7
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2" } */
> > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > >>> +
> > >>> +#include <stddef.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > >>> +}
> > >>> --
> > >>> 2.36.1
> > >>>
> > >
> > >
> > >
> > > --
> > > H.J.
>
>
>
> --
> H.J.



-- 
宋方睿

Re: [PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[Richard Biener]

On Thu, Jun 16, 2022 at 1:38 AM Fangrui Song <maskray@google.com> wrote:
>
> On Wed, Jun 15, 2022 at 2:44 PM H.J. Lu via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > On Mon, Jun 13, 2022 at 9:01 AM Richard Biener
> > <richard.guenther@gmail.com> wrote:
> > >
> > >
> > >
> > > > Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> > > >
> > > > On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> > > > <richard.guenther@gmail.com> wrote:
> > > >>
> > > >>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> > > >>> <gcc-patches@gcc.gnu.org> wrote:
> > > >>>
> > > >>> Add -fextra-libc-function=memcmpeq to map
> > > >>>
> > > >>> extern int __memcmpeq (const void *, const void *, size_t);
> > > >>>
> > > >>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
> > > >>
> > > >> Humm.  Can't we instead use the presence of a declaration
> > > >> of __memcmpeq with a GNU standard dialect as this instead of
> > > >> adding a weird -fextra-libc-function= option?  Maybe that's even
> > > >> reasonable with a non-GNU dialect standard in effect since
> > > >> __ prefixed names are in the implementation namespace?
> > > >
> > > > But not all source codes include <string.h> and GCC may generate
> > > > memcmp directly.  How should we handle these cases?
> > >
> > > Not.  Similar as to vectorized math functions.
> > > I think it’s not worth optimizing for this case.
> >
> > Another question.  Should we consider any __memcmpeq prototype
> > or just the one in the system header file?

Any.

> An idea from https://reviews.llvm.org/D56593#3586673: -fbuiltin-__memcmpeq
>
> This requires making -fbuiltin-function available, see
> https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
> ("There is no corresponding -fbuiltin-function option")
>
> I prefer an option over a magic behavior about whether a declaration exists.

But we already have this behavior for multiple cases.  It's also the only
way that in practice __memcmpeq will be used - _nobody_ (but maybe
special crafted SPEC peak runs) will add explicit -fbuiltin-__memcmpeq.

Richard.

> > > Richard.
> > >
> > > >
> > > >> Richard.
> > > >>
> > > >>> gcc/
> > > >>>
> > > >>>        * builtins.cc: Include "opts.h".
> > > >>>        (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
> > > >>>        available.
> > > >>>        * builtins.def (BUILT_IN___MEMCMPEQ): New.
> > > >>>        * common.opt: Add -fextra-libc-function=.
> > > >>>        * opts.cc (extra_libc_functions): New.
> > > >>>        (parse_extra_libc_function): New function.
> > > >>>        (common_handle_option): Handle -fextra-libc-function=.
> > > >>>        * opts.h (extra_libc_function_list): New.
> > > >>>        (extra_libc_functions): Likewise.
> > > >>>        * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
> > > >>>
> > > >>> gcc/testsuite/
> > > >>>
> > > >>>        * c-c++-common/memcmpeq-1.c: New test.
> > > >>>        * c-c++-common/memcmpeq-2.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-3.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-4.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-5.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-6.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-7.c: Likewise.
> > > >>> ---
> > > >>> gcc/builtins.cc                         |  5 ++++-
> > > >>> gcc/builtins.def                        |  4 ++++
> > > >>> gcc/common.opt                          |  4 ++++
> > > >>> gcc/doc/invoke.texi                     |  6 ++++++
> > > >>> gcc/opts.cc                             | 23 +++++++++++++++++++++++
> > > >>> gcc/opts.h                              |  7 +++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
> > > >>> 13 files changed, 125 insertions(+), 1 deletion(-)
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
> > > >>>
> > > >>> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> > > >>> index b9d89b409b8..22269318e8c 100644
> > > >>> --- a/gcc/builtins.cc
> > > >>> +++ b/gcc/builtins.cc
> > > >>> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
> > > >>> #include "demangle.h"
> > > >>> #include "gimple-range.h"
> > > >>> #include "pointer-query.h"
> > > >>> +#include "opts.h"
> > > >>>
> > > >>> struct target_builtins default_target_builtins;
> > > >>> #if SWITCHABLE_TARGET
> > > >>> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
> > > >>>        return target;
> > > >>>       if (fcode == BUILT_IN_MEMCMP_EQ)
> > > >>>        {
> > > >>> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> > > >>> +         tree newdecl = builtin_decl_explicit
> > > >>> +           (extra_libc_functions.has_memcmpeq
> > > >>> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
> > > >>>          TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
> > > >>>        }
> > > >>>       break;
> > > >>> diff --git a/gcc/builtins.def b/gcc/builtins.def
> > > >>> index 005976f34e9..eb8d33b16e9 100644
> > > >>> --- a/gcc/builtins.def
> > > >>> +++ b/gcc/builtins.def
> > > >>> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
> > > >>>    equality with zero.  */
> > > >>> DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
> > > >>>
> > > >>> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> > > >>> +   -fextra-libc-function=memcmpeq.  */
> > > >>> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> > > >>> +
> > > >>> /* An internal version of strcmp/strncmp, used when the result is only
> > > >>>    tested for equality with zero.  */
> > > >>> DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> > > >>> diff --git a/gcc/common.opt b/gcc/common.opt
> > > >>> index 7ca0cceed82..7a7631682b0 100644
> > > >>> --- a/gcc/common.opt
> > > >>> +++ b/gcc/common.opt
> > > >>> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
> > > >>> EnumValue
> > > >>> Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
> > > >>>
> > > >>> +fextra-libc-function=
> > > >>> +Common Driver Joined
> > > >>> +Specify the extra function in the C library.
> > > >>> +
> > > >>> ; Whether we permit the extended set of values for FLT_EVAL_METHOD
> > > >>> ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
> > > >>> fpermitted-flt-eval-methods=
> > > >>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > > >>> index 8cd5bdddc5d..fe1e3709953 100644
> > > >>> --- a/gcc/doc/invoke.texi
> > > >>> +++ b/gcc/doc/invoke.texi
> > > >>> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
> > > >>> -ffixed-@var{reg}  -fexceptions @gol
> > > >>> -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
> > > >>> -fasynchronous-unwind-tables @gol
> > > >>> +-fextra-libc-function=memcmpeq @gol
> > > >>> -fno-gnu-unique @gol
> > > >>> -finhibit-size-directive  -fcommon  -fno-ident @gol
> > > >>> -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> > > >>> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
> > > >>> table is exact at each instruction boundary, so it can be used for stack
> > > >>> unwinding from asynchronous events (such as debugger or garbage collector).
> > > >>>
> > > >>> +@item -fextra-libc-function=memcmpeq
> > > >>> +@opindex fextra-libc-function
> > > >>> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> > > >>> +@code{__builtin_memcmp_eq}.
> > > >>> +
> > > >>> @item -fno-gnu-unique
> > > >>> @opindex fno-gnu-unique
> > > >>> @opindex fgnu-unique
> > > >>> diff --git a/gcc/opts.cc b/gcc/opts.cc
> > > >>> index bf06a55456a..e77f0922acc 100644
> > > >>> --- a/gcc/opts.cc
> > > >>> +++ b/gcc/opts.cc
> > > >>> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
> > > >>> /* In this file all option sets are explicit.  */
> > > >>> #undef OPTION_SET_P
> > > >>>
> > > >>> +/* The list of extra functions in the C library.  */
> > > >>> +extra_libc_function_list extra_libc_functions;
> > > >>> +
> > > >>> static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
> > > >>>
> > > >>> /* Names of fundamental debug info formats indexed by enum
> > > >>> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
> > > >>>   return flags;
> > > >>> }
> > > >>>
> > > >>> +/* Parse -fextra-libc-function= suboptions from ARG.  */
> > > >>> +
> > > >>> +static void
> > > >>> +parse_extra_libc_function (const char *arg)
> > > >>> +{
> > > >>> +  /* Check to see if the string matches a sub-option name.  */
> > > >>> +  if (strcmp (arg, "memcmpeq") == 0)
> > > >>> +    {
> > > >>> +      extra_libc_functions.has_memcmpeq = 1;
> > > >>> +      return;
> > > >>> +    }
> > > >>> +
> > > >>> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> > > >>> +        arg);
> > > >>> +}
> > > >>> +
> > > >>> /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
> > > >>>
> > > >>> unsigned int
> > > >>> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
> > > >>>       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
> > > >>>       break;
> > > >>>
> > > >>> +    case OPT_fextra_libc_function_:
> > > >>> +      parse_extra_libc_function (arg);
> > > >>> +      break;
> > > >>> +
> > > >>>     case OPT_fprofile_generate_:
> > > >>>       opts->x_profile_data_prefix = xstrdup (arg);
> > > >>>       value = true;
> > > >>> diff --git a/gcc/opts.h b/gcc/opts.h
> > > >>> index a43ce66cffe..e8d8835ba23 100644
> > > >>> --- a/gcc/opts.h
> > > >>> +++ b/gcc/opts.h
> > > >>> @@ -345,6 +345,13 @@ struct cl_option_handlers
> > > >>> extern const char *opt_fstack_limit_symbol_arg;
> > > >>> extern int opt_fstack_limit_register_no;
> > > >>>
> > > >>> +/* The list of extra functions in the C library.  */
> > > >>> +struct extra_libc_function_list
> > > >>> +{
> > > >>> +  unsigned int has_memcmpeq : 1;
> > > >>> +};
> > > >>> +extern extra_libc_function_list extra_libc_functions;
> > > >>> +
> > > >>> /* Input file names.  */
> > > >>>
> > > >>> extern const char **in_fnames;
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..487f6cd98db
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <stddef.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..1773dc2bee1
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <string.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return memcmp (s1, s2, len) == 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..69c9537d572
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <string.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return memcmp (s1, s2, len);
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..a448312ea96
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2" } */
> > > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <stddef.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..4ef33a1c238
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2" } */
> > > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <string.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return memcmp (s1, s2, len) == 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..52304df7079
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <stddef.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..d59765894e7
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2" } */
> > > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <stddef.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > > >>> +}
> > > >>> --
> > > >>> 2.36.1
> > > >>>
> > > >
> > > >
> > > >
> > > > --
> > > > H.J.
> >
> >
> >
> > --
> > H.J.
>
>
>
> --
> 宋方睿

Re: [PATCH] Add -fextra-libc-function=memcmpeq for __memcmpeq

[H.J. Lu]

On Mon, Jun 20, 2022 at 2:39 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Thu, Jun 16, 2022 at 1:38 AM Fangrui Song <maskray@google.com> wrote:
> >
> > On Wed, Jun 15, 2022 at 2:44 PM H.J. Lu via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > On Mon, Jun 13, 2022 at 9:01 AM Richard Biener
> > > <richard.guenther@gmail.com> wrote:
> > > >
> > > >
> > > >
> > > > > Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> > > > >
> > > > > On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> > > > > <richard.guenther@gmail.com> wrote:
> > > > >>
> > > > >>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> > > > >>> <gcc-patches@gcc.gnu.org> wrote:
> > > > >>>
> > > > >>> Add -fextra-libc-function=memcmpeq to map
> > > > >>>
> > > > >>> extern int __memcmpeq (const void *, const void *, size_t);
> > > > >>>
> > > > >>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
> > > > >>
> > > > >> Humm.  Can't we instead use the presence of a declaration
> > > > >> of __memcmpeq with a GNU standard dialect as this instead of
> > > > >> adding a weird -fextra-libc-function= option?  Maybe that's even
> > > > >> reasonable with a non-GNU dialect standard in effect since
> > > > >> __ prefixed names are in the implementation namespace?
> > > > >
> > > > > But not all source codes include <string.h> and GCC may generate
> > > > > memcmp directly.  How should we handle these cases?
> > > >
> > > > Not.  Similar as to vectorized math functions.
> > > > I think it’s not worth optimizing for this case.
> > >
> > > Another question.  Should we consider any __memcmpeq prototype
> > > or just the one in the system header file?
>
> Any.

Here is the v2 patch:

https://gcc.gnu.org/pipermail/gcc-patches/2022-June/596881.html

> > An idea from https://reviews.llvm.org/D56593#3586673: -fbuiltin-__memcmpeq
> >
> > This requires making -fbuiltin-function available, see
> > https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
> > ("There is no corresponding -fbuiltin-function option")
> >
> > I prefer an option over a magic behavior about whether a declaration exists.
>
> But we already have this behavior for multiple cases.  It's also the only
> way that in practice __memcmpeq will be used - _nobody_ (but maybe
> special crafted SPEC peak runs) will add explicit -fbuiltin-__memcmpeq.
>
> Richard.

Thanks.

-- 
H.J.